Polypropylene fibres

ABSTRACT

A polypropylene fibre including a polypropylene blend comprising up to 15% by weight of sPP at least 10% by weight of a first isotactic polypropylene produced by a metallocene catalyst, and optionally a second isotactic polypropylene produced by a Ziegler-Natta catalyst.

FIELD OF THE INVENTION

The present invention relates to polypropylene fibres and to fabricsproduced from polypropylene fibres.

DESCRIPTION OF RELATED ART

Polypropylene is well known for the manufacture of fibres, particularlyfor manufacturing non woven fabrics.

EP-A-0789096 discloses such polypropylene fibres which are made of ablend of syndiotactic polypropylene (sPP) and isotactic polypropylene(iPP). That specification discloses that by blending from 0.3 to 3% byweight of sPP, based on the total polypropylene, to form a blend ofiPP-sPP, the fibres have increased natural bulk and smoothness, andnon-woven fabrics produced from the fibres have an improved softness.Moreover, that specification discloses that such a blend lowers thethermal bonding temperature of the fibres. Thermal bonding is employedto produce the non-woven fabrics from the polypropylene fibres.

The specification discloses that the isotactic polypropylene comprises ahomopolymer formed by the polymerisation of propylene by Ziegler-Nattacatalysis. The isotactic polypropylene typically has a weight averagemolecular weight Mw of from 100,000 to 4,000,000 and a number averagemolecular weight Mn of from 40,000 to 100,000, with a melting point offrom about 159 to 169° C. However, the polypropylene fibres produced inaccordance with this specification suffer from the technical problemthat the isotactic polypropylene, being made using a Ziegler-Nattacatalyst, does not have particularly high mechanical properties,particularly tenacity.

WO-A-96/23095 discloses a method for providing a non-woven fabric with awide bonding window in which the non-woven fabric is formed from fibresof a thermoplastic polymer blend including from 0.5 to 25 wt % ofsyndiotactic polypropylene. The syndiotactic polypropylene may beblended with a variety of different polymers, including isotacticpolypropylene. The specification includes a number of examples in whichvarious mixtures of syndiotactic polypropylene with isotacticpolypropylene were produced. The isotactic polypropylene comprisedcommercially available isotactic polypropylene, which is produced usinga Ziegler-Natta catalyst. It is disclosed in the specification that theuse of syndiotactic polypropylene widens the window of temperature overwhich thermal bonding can occur, and lowers the acceptable bondingtemperature.

WO-A-96/23095 also discloses the production of fibres from blendsincluding syndiotactic polypropylene which are either bi-componentfibres or bi-constituent fibres. Bi-component fibres are fibres whichhave been produced from at least two polymers extruded from separateextruders and spun together to form one fibre. Bi-constituent fibres areproduced from at least two polymers extruded from the same extruder as ablend. Both bi-component and bi-constituent fibres are disclosed asbeing used to improve the thermal bonding of Ziegler-Natta polypropylenein non-woven fabrics. In particular, a polymer with a lower meltingpoint compared to the Ziegler-Natta isotactic polypropylene, for examplepolyethylene, random copolymers or terpolymers, is used as the outerpart of the bi-component fibre or blended in the Ziegler-Nattapolypropylene to form the bi-constituent fibre.

EP-A-0634505 discloses improved propylene polymer yarn and articles madetherefrom in which for providing yarn capable of increased shrinkagesyndiotactic polypropylene is blended with isotactic polypropylene withthere being from 5 to 50 parts per weight of syndiotactic polypropylene.It is disclosed that the yarn has increased resiliency and shrinkage,particularly useful in pile fabric and carpeting. It is disclosed thatthe polypropylene blends display a lowering of the heat softeningtemperature and a broadening of the thermal response curve as measuredby differential scanning calorimetry as a consequence of the presence ofsyndiotactic polypropylene.

U.S. Pat. No. 5,269,807 discloses a suture fabricated from syndiotacticpolypropylene exhibiting a greater flexibility than a comparable suturemanufactured from isotactic polypropylene. The syndiotacticpolypropylene may be blended with, inter alia, isotactic polypropylene.

EP-A-0451743 discloses a method for moulding syndiotactic polypropylenein which the syndiotactic polypropylene may be blended with a smallamount of a polypropylene having a substantially isotactic structure. Itis disclosed that fibres may be formed from the polypropylene. It isalso disclosed that the isotactic polypropylene is manufactured by theuse of a catalyst comprising titanium trichloride and an organoaluminiumcompound, or titanium trichloride or titanium tetrachloride supported onmagnesium halide and an organoaluminium compound, i.e. a Ziegler-Nattacatalyst.

EP-A-0414047 discloses polypropylene fibres formed of blends ofsyndiotactic and isotactic polypropylene. The blend includes at least 50parts by weight of the syndiotactic polypropylene and at most 50 partsby weight of the isotactic polypropylene. It is disclosed that theextrudability of the fibres is improved and the fibre stretchingconditions are broadened.

EP-A-0894875 discloses bicomponent fibres of isotactic and syndiotacticpolypropylene in which an isotactic polypropylene component and asyndiotactic polypropylene component are each fused to the other alongthe fibre axis. This specification does not address the problem of themanufacture of non-woven fabrics by thermal bonding.

EP-A-0832924 relates to a polyolefin moulding composition for producinghigh strength non-woven fabric.

WO-A-97/10300 discloses polypropylene blend compositions comprisingpropylene copolymer having a broad molecular weight distribution. Thefirst and second propylene polymers of the blend are preferablyisotactic.

EP-A-0870779 discloses a metallocene catalyst system for producing apolypropylene blend of iso- and syndiotactic polypropylene.

EP-A-0284707 discloses a hafnium metallocene catalyst for thepolymerisation of olefins, in particular to make isotacticpolypropylene.

EP-A-0427696 discloses a process and catalyst for producing syndiotacticpolymers, in particular syndiotactic polypropylene using metallocenecatalysts.

It is further known to produce syndiotactic polypropylene usingmetallocene catalysts as has been disclosed for example in U.S. Pat. No.4,794,096.

Recently, metallocene catalysts have also been employed to produceisotactic polypropylene. Isotactic polypropylene which has been producedusing a metallocene catalyst is identified hereinafter as miPP. Fibresmade of miPP exhibit much higher mechanical properties, mainly tenacity,than typical Ziegler-Natta polypropylene based fibres, hereinafterreferred to as znPP fibres. However, this gain in tenacity is onlypartly transferred to non-woven fabrics which have been produced fromthe miPP fibres by thermal bonding. Indeed, fibres produced using miPPhave a very narrow thermal bonding window, the window defining a rangeof thermal bonding temperatures through which, after thermal bonding ofthe fibres, the non-woven fabric exhibits the best mechanicalproperties. As a result, only a small number of the miPP fibrescontribute to the mechanical properties of the non-woven fabric. Also,the quality of the thermal bond between adjacent miPP fibres is poor.Thus known miPP fibres have been found to be more difficult to thermallybond than znPP fibres, despite a lower melting point.

SUMMARY OF THE INVENTION

It is an aim of the present invention to broaden the thermal bondingwindow of miPP fibres. It is a further aim of the invention to providenon-woven fabrics of miPP fibres exhibiting improved mechanicalproperties, in particular tenacity.

It is known that polypropylene fibres, and non-woven fabrics made ofpolypropylene fibres, tend to feel rough to the touch. It is also an aimof the present invention to improve the softness of miPP polypropylenefibres.

The present invention provides a polypropylene fibre including apolypropylene blend comprising up to 15% by weight of sPP, at least 10%by weight of a first isotactic polypropylene produced by a metallocenecatalyst, and optionally a second isotactic polypropylene produced by aZiegler-Natta catalyst.

Preferably, the sPP concentration in the sPP/miPP blend is from 3 to 15wt %. The fibre may be a two component sPP/miPP blend, including atleast 85 wt % miPP. When present, the znPP may be a homopolymer,copolymer or terpolymer.

Preferably, the miPP is a homopolymer, copolymer, being either a randomor block copolymer, or terpolymer of isotactic polypropylene produced bya metallocene catalyst.

Preferably, the first polypropylene has a dispersion index (D) of from 2to 3.5. Preferably, the first polypropylene has a melting temperature inthe range of from 140 to 155° C. for homopolymer and a meltingtemperature of from 80 to 150° C. for a copolymer or terpolymer.

The miPP preferably has a melt flow index (MFI) of from 1 to 2500 g/10mins. In this specification the MFI values are those determined usingthe procedure of ISO 1133 using a load of 2.16 kg at a temperature of230° C.

More preferably, the first polypropylene homopolymer has an Mn of from50,000 to 100,000 kDa and the MFI may range from 15 to 90 g/10 min forspunlaid or staple fibres. The MFI may range from 350 to 2500 g/10 minfor the first polypropylene being a copolymer or a terpolymer having ahigher Mn than for the homopolymer for making melt blown fibres.

The sPP is preferably a homopolymer or a random copolymer with acomonomer content of from 0.1 to 1.5 wt %. The sPP may alternatively bea block copolymer having a higher comonomer content, or a terpolymer. Ifthe comonomer content is above 1.5 wt %, the sPP tends to become sticky,thus resulting in problems when spinning the fibres or thermally bondingthe fibres. The comonomer content is selected so as to decrease themelting point of the sPP iPP blend below 130° C. A lower melting pointcan also be obtained by using particular catalysts and/or processconditions during polymerisation of the sPP. Preferably, the sPP has amelting temperature of up to about 130° C. The sPP typically has twomelting peaks, one being around 112° C. and the other being around 128°C. The sPP typically has an MFI of from 0.1 to 1000 g/10 min, moretypically from 1 to 60g/10 min. The sPP may have a monomodal ormultimodal molecular weight distribution, and most preferably is abimodal polymer in order to improve the processability of the sPP. Theproperties of a typical bimodal sPP for use with the invention arespecified in Table 1.

The present invention further provides a polypropylene fibre including apolypropylene blend comprising up to 15% by weight of sPP, at, least 10%by weight of a first isotactic polypropylene homopolymer, copolymer orterpolymer having a melting temperature of from 80° C. to 155° C., andoptionally a second isotactic polypropylene homopolymer or copolymerhaving a melting temperature of from 159° C. to 169° C.

Preferably, the first isotactic polypropylene has a dispersion index (D)of from 2 to 3.5.

Preferably, the second isotactic polypropylene has a dispersion index(D) of from 3 to 9.

The present invention further provides a fabric produced from thepolypropylene fibre of the invention.

The present invention yet further provides a product including thatfabric, the product being selected from among others a filter, personalwipe, diaper, feminine hygiene product, incontinence product, wounddressing, bandage, surgical gown, surgical drape and protective cover.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is predicated on the discovery by the presentinventor that when blended with miPP, even in small concentrations, sPPis rejected to the surface of the polypropylene fibres during thespinning process. Accordingly, when blending miPP, which has a typicalmelting range of from around 140C to around 155° C., with sPP, whichtypically has a melting range of from about 80° C. to about 130° C.,even though only a small concentration of sPP is incorporated into themiPP, as a result of the rejection of the sPP to the surface of thefibres, the range of temperature through which the fibres can bethermally bonded, is broadened and shifted to lower temperatures. As aconsequence, at any given thermal bonding temperature, more fibres arethermally bonded and bonding strength improves, thereby improving themechanical properties of the non-woven fabric produced thereby.

Since the sPP has a melting peak about 15° C. lower than that of themiPP and is rejected to the surface of the fibres during the spinningprocess, as a consequence when thermally bonding the fibres at a lowertemperature than the optimal thermal bonding temperature for pure miPPfibres, the sPP contributes to improving the strength of the thermallybonded points, hence broadening the thermal bonding window.

The present inventor has found that when used in an amount of only about2 to 3 wt % sPP in the sPP/miPP blend, the thermal bondability isincreased, as a result of the sPP being rejected to the surface of thefibres during the spinning process. The known Ziegler-Natta isotacticpolypropylene fibres, such as those disclosed in the patentspecifications identified hereinabove, typically have a meltingtemperature of around 159-169° C., for example 162° C. The difference intemperature between the known Ziegler-Natta isotactic polypropylenefibres and the sPP incorporated therein in the patent specificationsreferred to hereinabove has provided improved properties. However, formiPP utilised in accordance with the present invention, the typicalmelting point is around 140° C. to 155° C., which is typically around15° C. to 20° C. higher than that for the sPP, but also significantlylower than that of the Ziegler-Natta isotactic polypropylene.

Comonomer addition into the sPP allows the melting point to decrease. Asa consequence, comonomer concentration may be adjusted to reach thedesired melting temperature, whereby the miPP and the sPP have a meltingpeak difference of about 15° C. to 20° C. The combination of therelatively low melting peak difference between on the one hand the miPPand on the other hand the sPP and also the provision of the sPP on thesurface of the fibres following the spinning process providessignificant advantages when the fibres are employed to make thermallybonded non-woven fabrics. An industrial thermal bonding process forproducing a non-woven fabric employs the passage at high speed of alayer of fibres to be thermally bonded through a pair of heated rollers.This process thus requires rapid and uniform melting of the surfaces ofadjacent fibres in order for a strong and reliable thermal bond to beachieved. The addition of sPP to the miPP lowers the thermal bondingtemperature of the fibres and broadens the thermal bonding temperaturerange or “window” for the fibres, thus increasing the ease of thermalbonding the fibres together. Since the sPP tends to be at the surface ofthe fibres and since the miPP has a melting point range which is onlyslightly higher than that of the sPP so that there is a meltingtemperature overlap between the sPP and the miPP in the thermal bondingtemperature window, when the fibres are thermally bonded, which can beachieved at lower-temperatures than for miPP alone, the increasedbreadth of the thermal bonding window can provide that not only is thesPP on the surface of the fibres melted, but also some of the miPP tendsto be melted, to form bonds between adjacent fibres. Thus theincorporation of sPP into miPP enables the maximum strength of thenon-woven fabric to be greatly increased as a result of this increasedthermal bond formation between adjacent fibres.

In contrast, znPP has a significantly higher melting point range thanthat for sPP so that when the known znPP/sPP fibres are thermallybonded, the thermal bonding, and thus the tenacity are lower than forthe miPP/sPP blends of the invention because the znPP does notcontribute to the formation of thermal bonds.

The miPP employed in accordance with the invention has a narrowmolecular weight distribution, typically having a dispersion index D offrom 2 to 3.5, more preferably from 2 to 3. The dispersion index D isthe ratio Mw/Mn, where Mw is the weight number average molecular weightand Mn is the number average molecular weight of the polymer. The miPPtypically has a peak in the molecular weight distribution of 60,000 to120,000 kDa. The miPP has a melting temperature in the range of from140° C. to 155° C. The properties of two typical miPP resins for use inthe invention are specified in Table 1.

In contrast, the sPP has a slightly broader molecular weightdistribution than for the miPP, wherein typically D may be around 4 andhas a peak of the molecular weight distribution at around 20,000 to40,000 kDa. The sPP has a melting temperature of up to about 130° C. Inview of the separation between the peaks and the substantial non-overlapof the molecular weight distributions of the sPP and the miPP, it issurprising that those two components can in fact readily be blendedtogether. The sPP tends to be provided at the surface of the miPPfibres. As stated above, this provides an advantage in thermal bonding.Since there is an overlap in the melting point range in the miPP and thesPP, there is an increase in thermal bonding between the fibres, andthis increase is manifested in an increase tenacity for non-wovenfabrics produced in accordance with the invention, with tenacityincreasing with an increase in the amount of sPP. This is because anyincrease in sPP tends to be increase the amount of material thermallybonded on the surface of the fibres. However, for sPP amounts greaterthan about 15 to 20 wt %, the amount varying depending upon otherparameters, such as the particular processing conditions for spinningthe fibres, the tenacity can tend to decrease.

The addition of sPP to the miPP also has been found by the inventor toimprove the softness of the fibres. As a result of this surfacerejection phenomenon, the inventor has found that the softness of thefibres may be increased using only small amounts of sPP, for examplefrom 0.3 wt % sPP in the sPP/miPP blend. Since the blending of sPP intomiPP permits a lower thermal bonding temperature to be employed thanwould be employed for pure miPP fibres, and since lower thermal bondingtemperatures tend to reduce the roughness to the touch of a non-wovenfabric produced from the fibres, introducing sPP in accordance with theinvention into miPP improves the softness of the non-woven fabric.

Furthermore, in accordance with the invention when sPP is incorporatedinto miPP to form blends thereof, and when those blends are used toproduce spun fibres, the sPP promotes fibres having improved naturalbulk, resulting in improved softness of the non-woven fabric.

In addition, the use of miPP in blends with sPP in accordance with theinvention tends to provide fibres which can be more readily spun ascompared to known znPP fibres. The substantial absence of such longchains in the molecular weight distribution of the miPP tends to reducebuilt-in stress during spinning thereby to allow in an increase in themaximum spin speed for the fibres of the sPP/miPP blends in accordancewith the invention.

In accordance with the invention, the incorporation of sPP into miPP toform blends thereof provides a broader thermal bonding window, allowingtransfer of the properties of the miPP fibres into the properties of thenon-woven fabrics produced from the blends. The thermal bondingtemperature of fibres produced from such blends is also slightly lower.The fibres and non-woven fabrics produced from the blends have increasedsoftness and the spun fibres have natural bulk as a result of theintroduction of sPP into the miPP. The fibres also have improvedresiliency compared to known polypropylene znPP fibres as a result ofthe use of sPP. Furthermore, the use of miPP allows the production offiner fibres, resulting in softer fibres and a more homogeneousdistribution of the fibres in the non-woven fabric.

Although it was known prior to the present invention to use a secondpolymer in fibres, it has not heretofore been proposed to employ sPP ina blend with miPP for the production of fibres. The use of sPP providesoptimum thermal characteristics that help improve the thermal bonding ofthe miPP fibres. Efficient thermal bonding of the fibres is required totransfer the outstanding mechanical properties of miPP fibres intonon-woven fabrics. In addition, only a few percent of sPP is enough toobserve a significant improvement in the mechanical properties such asthermal bondability and softness of the fibres and non-woven fabrics,whereas with other polymers much larger quantities are required. As aconsequence, the spinnability of the fibres produced using sPP/miPPblends in accordance with the invention is not significantly modified ascompared to known fibres.

The fibres produced in accordance with the invention may be eitherbi-component fibres or bi-constituent fibres. For bi-component fibres,miPP and sPP are fed into two different extruders. Thereafter the twoextrudates are spun together to form single fibres. For thebi-constituent fibres, blends of sPP/miPP are obtained by: dry blendingpellets, flakes or fluff of the two polymers before feeding them into acommon extruder; or using pellets or flakes of a blend of sPP and miPPwhich have been extruded together and then re-extruding the blend from asecond extruder.

When the blends of sPP/miPP are used to produce fibres in accordancewith the invention, at up to 15 wt % sPP there is no significant effecton the spinning characteristics of the blends. For the production ofspunlaid fibres, a typical extrusion temperature would be in the rangeof from 200° C. to 260° C., most typically from 230° C. to 250° C. Forthe production of staple fibres, a typical extrusion temperature wouldbe in the range of from 230° C. to 330° C., most typically from 280° C.to 300° C.

The fibres produced in accordance with the invention may be producedfrom sPP/miPP blends having other additives to improve the mechanicalprocessing or spinnability of the fibres. The fibres produced inaccordance with the invention may be used to produce non-woven fabricsfor use in filtration; in personal care products such as wipers,diapers, feminine hygiene products and incontinence products; in medicalproducts such as wound dressings, surgical gowns, bandages and surgicaldrapes; in protective covers; in outdoor fabrics and in geotextiles.Non-woven fabrics made with the sPP/miPP fibres of the invention can bepart of such products, or constitute entirely the products. As well asmaking non-woven fabrics, the fibres may also be employed to make aknitted fabric or a mat. The non-woven fabrics produced from the fibresin accordance with the invention can be produced by several processes,such as air through blowing, melt blowing, spun bonding or bonded cardedprocesses. The fibres of the invention may also be formed as a non-wovenspunlace- product which is formed without thermal bonding by fibresbeing entangled together to form a fabric by the application of a highpressure-fluid such as air or water.

The present invention will now be described in greater detail withreference to the following non-limiting examples.

EXAMPLES 1 AND 2 AND COMPARATIVE EXAMPLE 1

A non-woven fabric made using fibres of a polypropylene produced using aZiegler-Natta catalyst and having a weight of 17 g/m² was tested todetermine its tenacity in accordance with Comparative Example 1. Inaccordance with Examples 1 and 2, two isotactic polypropylenes producedusing a metallocene catalyst and having respectively 1 and 5 wt % sPPblended in the miPP, the non-woven fabrics also having a weight of 17g/m², were also tested for their tenacity. The non-woven fabrics wereall spun laid. For each of the three non-woven fabrics, the force atbreak in the machine direction and the force at break in the transversedirection were measured and the results are shown in Table 2.

Also shown in Table 2 is an indication of the bonding index, which is ameasure of the average properties of a non-woven fabric and iscalculated as the square root of the force at break in the machinedirection multiplied by the force at break in the transverse direction.The bonding index is normalised to a value of the weight of thenon-woven fabric.

It may be seen that for both the non-woven fabrics in accordance withExamples 1 and 2, the force at break in both the machine direction andin the transverse direction was higher than for the non-woven fabricproduced from the Ziegler-Natta polypropylene fibres of ComparativeExample 1. The bonding index is thus also higher for Examples 1 and 2 ascompared to Comparative Example 1. It may also be seen that as theamount of the sPP in the blend of miPP/sPP increases from 1% to 5% byweight going from Example 1 to Example 2, the force at break both in themachine direction and in the transverse direction, and also the bondingindex, increase. This shows that the tenacity of the non-woven fabricincreases with increase in the amount of sPP in the blend.

COMPARATIVE EXAMPLES 2 to 5

In Comparative Examples 2 and 4, non-woven fabrics composed of isotacticpolypropylene fibres produced using a Ziegler-Natta catalyst and havingrespective weights of 18 and 86 g/m² were tested to determine theirtenacity by measuring the force at break in the machine direction of thenon-woven fabric. The results are shown in Table 3. For ComparativeExamples 3 and 5, sPP was blended into the iPP to form a 95 iPP/5 sPPblend by weight and two non-woven fabrics were produced from fibres ofthose blends, the non-woven fabrics of Comparative Examples 3 and 5having the same weights of 18 g/m² and 86 g/m² as Comparative Examples 2and 4 respectively. Again, those non-woven fabrics were tested for theirtenacity and the results are shown in Table 3.

It may be seen from Table 3 that for each of the two different fabricweights, the blending of sPP into the Ziegler-Natta iPP did not tend toincrease the force at break, representing the tenacity, of the thermallybonded non-woven fabric.

The addition of sPP to znPP in accordance with the Comparative Examplesthus tends not to increase the maximum force at break which isachievable by non-woven fabrics thermally bonded from such fibres.However, as recognised in the prior art the addition of sPP to znPP doestend to reduce the thermal bonding temperature of the fibres, and alsobroadens the thermal bonding temperature window. However, the reductionin the bonding temperature and the increase in the breadth of thewindow, while increasing the ease of bonding, does not lead to anincrease in the maximum achievable thermal bond strength by adding sPPto znPP. Rather, the addition of sPP to znPP merely shifts the bondingtemperature at which the maximum strength is achieved, not the totalmaximum strength value itself, as evidenced by Comparative Examples 2 to5.

TABLE 1 sPP miPP1 miPP2 MI₂ 3.6 32 15 Tm ° C. 110 and 127 148.7 143.7 MnkDa 37426 54776 68556 Mw kDa 160229 137423 186430 Mz kDa 460875 242959400210 Mp kDa 50516 118926 134554 D 4.3 2.5 2.7

TABLE 2 Comparative Example 1 Example 1 Example 2 Property Ziegler-NattaPP miPP-1% sPP miPP-5% sPP Force at break in 3050 3245 3930 machinedirection (MD) (g/50 mm) Force at break in 2783 3523 3353 transversedirection (TD (g/50 mm) Bonding Index 2919 3381 3630

TABLE 3 Com- Com- parative Comparative parative Comparative Example 2Example 3 Example 4 Example 5 Non-woven iPP iPP/sPP iPP iPP/sPPComposition (95/5) (95/5) Weight 18 g/m² 18 g/m² 86 g/m² 86 g/m² Max.Force (N) 21 21 68 66 (MD)

What is claimed is:
 1. A polypropylene fibre including propylene blendcomprising a syndiotactic polypropylene in an amount of up to 15% byweight and at least 10% by weight of a first isotactic polypropylenehaving a melting temperature of from 80° C. to 155° C., and optionally asecond isotactic polypropylene having a melting temperature of from 159°C. to 169° C. wherein the first isotactic polypropylene has a dispersionindex (D) of from 2 to 3.5.
 2. A polypropylene fibre according to claim1 containing the second isotactic polypropylene having a dispersionindex (D) of from 3 to
 9. 3. A polypropylene fibre comprising a blend ofa syndiotactic polypropylene (sPP) and an isotactic polypropylene (miPP)produced by a metallocene catalyst, said sPP being present in saidpolypropylene blend in an amount of up to 15% by weight and saidisotactic polypropylene being present in said blend in an amount of atleast 10% by weight.
 4. A polypropylene fibre according to claim 3wherein the sPP concentration in the blend is from 3 to 15 wt %.
 5. Apolypropylene fibre according to claim 4 wherein the isotacticpolypropylene miPP has a dispersion index (D) of from 2 to 3.5.
 6. Apolypropylene fibre according to claim 5 wherein the isotacticpolypropylene miPP has a melting temperature in the range of from 80 to155° C.
 7. A polypropylene fibre according to claim 3 wherein theisotactic polypropylene miPP-has a melt flow index (MFI) of from 1 to2500 g/10 mins.
 8. A polypropylene fibre according to claim 7 whereinthe sPP has a melting temperature of up to about 130° C.
 9. Apolypropylene fibre according to claim 3 wherein the sPP has an MFI offrom 0.1 to 1000 g/10 min.
 10. A polypropylene fibre according to claim9 wherein the sPP has an MFI of from 1 to 60 g/10 min.
 11. Apolypropylene fibre according to claim 3 wherein the sPP has a monomodalor multimodal molecular weight distribution.
 12. A polypropylene fibreaccording to claim 3 wherein the sPP is preferentially located at thesurface of said fibre.
 13. A polypropylene fibre according to claim 3which is produced by a spinning process in which the sPP is rejected tothe surface of the fibre.
 14. A polypropylene fibre according to claim 3wherein the sPP is present in an amount of at least 0.3 wt %.
 15. Apolypropylene fibre according to claim 3 containing from about 2 toabout 3 wt % sPP.
 16. A polypropylene fibre according to claim 3 furthercomprising a second isotactic polypropylene produced (znPP) by aZiegler-Natta catalyst.
 17. A polypropylene fibre according to claim 16wherein the sPP has a melting peak which is at least about 15° C. lowerthan that of the miPP.
 18. A polypropylene fibre comprising apolypropylene blend of a syndiotactic polypropylene (sPP) in an amountof up to 15% by weight and at least 10% by weight of a first isotactic(miPP) polypropylene produced by a metallocene catalyst having a meltingtemperature of from 80° C. to 155° C., and optionally a second isotacticpolypropylene (znPP) produced by a Ziegler-Natta catalyst and having amelting temperature of from 159° C. to 169° C.
 19. A polypropylene fibreaccording to claim 18 wherein the sPP is preferentially located at thesurface of said fibre.
 20. A polypropylene fibre according to claim 19further comprising said second isotactic polypropylene (znPP) which hasa dispersion index of from 3 to
 9. 21. A fabric produced from thepolypropylene fibre according to claim
 18. 22. A product including afabric according to claim 21, the product being selected from a filter,personal wipe, diaper, feminine hygiene product, incontinence product,wound dressing, bandage, surgical gown, and surgical drape.